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Phy 231
Your 'cq_1_12.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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Masses of 5 kg and 6 kg are suspended from opposite sides of a light frictionless pulley and are released.
• What will be the net force on the 2-mass system and what will be the magnitude and direction of its acceleration?
answer/question/discussion: ->->->->->->->->->->->-> :
Fnet= 5kg * 9.8cm/s^2= 49N , Fnet= 6kg * 9.8cm/s^2= 58.8N
58.8N - 49N= 9.8N= Fnet on the system
a= Fnet/m= 9.8N/11kg= .891m/s^2 in the positive direction, the 6kg mass goes down
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• If you give the system a push so that at the instant of release the 5 kg object is descending at 1.8 meters / second, what will be the speed and direction of motion of the 5 kg mass 1 second later?
answer/question/discussion: ->->->->->->->->->->->-> :
Was the 1.8m/s suppose to be 1.8m/s^2?
1.8m/s^2 - .891m/s^2= .909m/s^2 after 1sec in the negative direction (5kg mass going down)
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@& The rate of descent would be a rate of change of position, or a velocity.
An object doesn't descent at 1.8 m/s^2; its velocity might change at a rate of 1.8 m/s^2, but a rate of change of velocity is not a rate of descent.
If the acceleration of an object (i.e., the rate of change of its velocity) changed from .891 m/s^2 to 1.8 m/s^2, then .909 m/s^2 would be the change in its acceleration. However it wouldn't be a change in velocity, and it wouldn't be a change in position.
In this question, though, the net force and mass are unchanging, so the acceleration is uniform.*@
• During the first second, are the velocity and acceleration of the system in the same direction or in opposite directions, and does the system slow down or speed up?
answer/question/discussion: ->->->->->->->->->->->-> :
Since the 6kg is falling, shouldn’t the velocity and acceleration of the system be in the same direction? And the system would speed up by .891m/s^2 each second that the 6kg mass is falling.
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@& The system isn't rising or falling, since one mass is rising while the other is falling.
The acceleration is in the direction in which the 6 kg mass is falling.
In the present situation is the 6 kg mass rising or falling?
Is the acceleration therefore in the same direction as the motion or opposite?*@
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